1. Technical Field
The present invention relates to a technique for compensating for an error in characteristics (particularly, a threshold voltage) of transistors in a pixel circuit.
2. Related Art
JP-A-2009-48202 discloses a technique for compensating for an error in characteristics (a threshold voltage or a mobility) of a driving transistor used to drive an organic EL element. FIG. 23 is a circuit diagram of a pixel circuit 90 disclosed in JP-A-2009-48202 (FIG. 11). During a writing period when a grayscale potential corresponding to a designated grayscale is supplied to an electrode 93 of a capacitive element 92 via a switch 91, a gate and a drain of a driving transistor 94 are connected (diode-connected) to each other through a switch 95 in a state where the driving transistor 94 is maintained to be turned on. Therefore, a gate-source voltage of the driving transistor 94 is set to a voltage Vrst which compensates for an error in the threshold voltage VTH thereof. In addition, during a driving period after the writing period has elapsed, a driving potential with a triangular waveform is supplied to the electrode 93 of each pixel circuit 90, and thereby a light emitting time of a light emitting element 97 connected to a circuit point 96 is controlled to be varied according to the designated grayscale.
However, it is difficult to apply the technique disclosed in JP-A-2009-48202 to a configuration in which a high resistance electro-optical element such as an electrophoresis element or a liquid crystal element is connected to the circuit point 96. This is because since a current hardly flows through the electro-optical element, a potential at the circuit point 96 is not determined, and thus the gate-source voltage of the driving transistor 94 does not converge to the target voltage Vrst even if the driving transistor 94 and the switch 95 are controlled to be in a turned-on state during the writing period.